Site U1451

Site U1453

“…The ash layer falls off the main trend defined by lithologies in the two measured core sections, which shows a relatively simple binary mixing trend (Figure F14). This mixing relationship is consistent with parallel observations at Sites U1451 and U1452 for mixing between a marine biogenic carbonate end-member and a terrigenous silicate component with a higher Sr/Ca ratio (see Geochemistry and microbiology in the Site U1451 chapter and Geo-chemistry and microbiology in the Site U1452 chapter [France-Lanord et al, 2016b, 2016c). Section 31F-2 (155.6-156.9 m CSF-A) was also scanned at high resolution by spot XRF and contains a reversed to normal to reversed transition identified by paleomagnetic stratigraphy as the Jaramillo Subchron (0.988-1.072 Ma; see Paleomagnetism).…”

“…Two core sections from hemipelagic calcareous clay Unit III (Lithostratigraphy) were scanned at high resolution using handheld X-ray fluorescence (XRF) for a total of 38 spot analyses (Section 354-U1453A-30F-3, 152.5-153.5 m CSF-A; Section 31F-2, 155.6-156.9 m CSF-A) ( Table T13; see Geochemistry and microbiology in the Expedition 354 methods chapter and Geochemistry and microbiology in the Site U1451 chapter [France-Lanord et al, 2016a, 2016b). The semiquantitative (uncalibrated) Ca abundances in these two core sections measured by XRF range from 0.3 wt% (volcanic ash) to 14.8 wt% Ca (calcareous clay), corresponding to a wide range of calculated carbonate contents (CaCO 3 = <2 to ~60 wt%) consistent with the silt, clay, calcareous clay, and ash lithologies present.…”

Data report: paleomagnetic directions from IODP Expedition 354, Hole U1451A, Cores 23H and 24H

“…Although all sites recovered at least middle to late Pleistocene sediments, three sites were drilled deeper than 800 m drilling depth below seafloor, Method A (CSF-A), to investigate the Neogene and older Bengal Fan and/or pre-Bengal Fan deposits. The easternmost site, U1451, drilled on the western flank of the Ninetyeast Ridge, recovered the longest continuous record of Bengal Fan sedimentation, stretching back to at least the Oligocene (see the Site U1451 chapter [France-Lanord et al, 2016c]).…”

“…L* and magnetic susceptibility signals reflecting cyclical relative contribution of biogenic carbonate are similar to bettercharacterized middle and late Pleistocene Lower Bengal Fan hemipelagic sediments deposited at 1-2 cm/ky (e.g., Weber et al, 2018), as opposed to higher accumulation rate turbiditic sediments that suggest this interval could record ~0.8-1.6 My of deposition. Paleomagnetic measurements conducted on board the R/V JOIDES Resolution with the superconducting rock magnetometer (SRM) revealed scattered directions that are likely the result of a weak natural remanent magnetization (NRM) and coring artifacts (see the Site U1451 chapter [France-Lanord et al, 2016c]). Shipboard calcareous nannofossil biostratigraphy identified the last occurrence of Discoaster pentaradiatus (2.39 Ma) between the core catchers of Cores 21F and 22H and the last occurrence of Discoaster surculus (2.49 Ma) and Reticulofenestra pseudoumbilicus (3.70 Ma) between the core catchers of Cores 24H and 25H.…”

“…Shipboard calcareous nannofossil biostratigraphy identified the last occurrence of Discoaster pentaradiatus (2.39 Ma) between the core catchers of Cores 21F and 22H and the last occurrence of Discoaster surculus (2.49 Ma) and Reticulofenestra pseudoumbilicus (3.70 Ma) between the core catchers of Cores 24H and 25H. Shipboard planktonic foraminifer biostratigraphy identified the last occurrence of Dentoglobigerina altispira (3.47 Ma) between the core catchers of Cores 23H and 24H (see the Site U1451 chapter [France-Lanord et al, 2016c]; Gradstein et al, 2012). Although postexpedition research is in progress to refine the biostratigraphy, the locations of these biomarkers suggest that Cores 23H and 24H could contain magnetic reversals of the Gauss Chron and/or the Gauss/Matuyama boundary, which would provide strong tie points to the geomagnetic polarity timescale (GPTS) and constraints on the Pliocene/Pleistocene boundary, thus motivating a more detailed magnetostratigraphic study.…”